Conventional 3D displays usually provide views of a 3D scene for a fixed single position. Those 3D displays that permit viewing from multiple positions and can hence be termed holographic tend to suffer from limited 3D resolution and the viewing experience tends to change from one view to another. Conventional 3D volumetric displays, such as those that project 2D images onto rotating screens or that project images onto water vapor and so forth, tend to suffer from various shortcomings with respect to occlusion, depth of view, distorted field of view, and the like.
Various approaches have been taken in an attempt to provide a truly holographic mid-air display. Some approaches use rotating mirrors and a laser to project low resolution 3D holographic images by ionizing air, while yet others use a special medium such as vapor saturated gas to support the images. One of the major challenges currently has been to make high resolution 3D holographic displays viable in mid-air without the need for delicate mechanical parts such as rotating Galvanometric mirrors and the like, or without requiring a special medium to support the display.